Treatment method of complex waste

Abstract

The invention relates to a method for treating a mixture M1, said method comprising the following steps: a) a pressurizing step: pressurizing said mixture M1 to obtain a mixture M1p; b) a heating step of heating the mixture M1p to allow a mixture M2 to be obtained; c) a separation step: separating the mixture M2 to obtain an inorganic-rich stream M3 and an inorganic-poor stream M4; d) a hydrothermal gasification step: carrying out hydrothermal gasification on the inorganic-poor material flow M4 to obtain a mixture M5; e) a cooling and separation step of cooling and separating at least a portion of the mixture M5 to separate the gas from a liquid effluent M5'comprising ammonia; f) a possible ammonia enrichment step: subjecting at least a portion of the liquid effluent M5'to an ammonia enrichment treatment to obtain an ammonia-rich stream M5 ''and an ammonia-lean stream M8; g) a mixing step of mixing (i) at least a portion of the stream M3 and (ii) at least a portion of the stream M5'or at least a portion of the stream M5 ", if any, obtained by step f), to obtain a mixture M6; h) a struvite formation step of forming struvite from at least a portion of the mixture M6 in a precipitation reactor; and i) a struvite recovery step: recovering struvite at an outlet of the precipitation reactor. The treatment method further comprises at least one injection step of injecting at least one magnesium salt into the mixture M1 before step a) and / or during step g) and / or during step h) and / or into the mixture M6 between steps g) and h), the mixing step g) may be carried out in the precipitation reactor as desired.

Description

Technical Field

[0001] The present invention relates to the field of treatment of complex wastes comprising organic and inorganic matter, such as aqueous wastes, sewage sludge and sewage sludge. Prior art

[0002] Wastewater treatment is necessary for environmental protection. A purification plant (or sewage treatment plant) consists of two main parts, namely the treatment of wastewater and the treatment of sludge produced by water treatment.

[0003] The goal of wastewater treatment is to eliminate pollution, in particular particle (also called suspended matter) pollution, especially carbon, nitrogen and phosphorus pollution. Purification plants also make it possible to recover resources (such as phosphorus) or to generate energy, for example by producing biogas.

[0004] Resource recovery has now become a concern as many types of elements are approaching shortages: recovering these elements seems increasingly critical.

[0005] This is the case with phosphorus, which is included in the EU list of critical raw materials due to the gradual depletion of phosphate mines, the increasing demand and the irreplaceable nature of phosphorus. Phosphorus is therefore a fertilizer element that is essential and irreplaceable for crops. It is therefore desirable to recover phosphorus to the greatest extent possible.

[0006] Therefore, a major focus is on recovering phosphorus in purification plants.

[0007] Sludge from purification plants has been considered as a source of supplementary phosphorus.

[0008] Application to land is considered the most practical option, but this has sparked growing public concern about contaminants in sludge, such as pathogens, heavy metals, persistent organic pollutants and micropollutants.

[0009] Thermochemical treatment of sludge, especially incineration, appears to be an alternative to conventional elimination routes. It has significant advantages such as deodorization, high efficiency, substantial waste volume reduction (about 90%), destruction of organic pollutants and inactivation of pathogens. More importantly, incineration produces a solid residue in the form of ash, whose phosphorus (P) concentration (9-13%) is comparable to that of phosphate rock.

[0010] However, the ash produced by sludge incineration consists of a complex mineral matrix in which phosphorus accumulates together with heavy metals, making it impossible to use these ashes directly as fertilizers. In addition, the bioavailability of phosphorus in the ash is limited due to its binding to minerals. Therefore, the removal of heavy metals and the improvement of phosphorus bioavailability become economically and ecologically laborious processes to recover phosphorus from the ash.

[0011] Therefore, there is an urgent need to propose an alternative process that allows the direct recovery of phosphorus from sludge in a bioavailable form, such as struvite, and limits the concentration of heavy metals contained through a precipitation step, while adopting a sustainable way. Summary of the invention

[0012] The present invention relates to a method for treating a mixture M1 containing at least organic matter, the method comprising the following steps:

[0013] a) a pressurization step: pressurizing the mixture M1 to a pressure of 150 to 300 bar, preferably 170 to 210 bar, to obtain a mixture M1p;

[0014] b) a heating step: heating the mixture M1p to a temperature of 250° C. to 500° C. to obtain a mixture M2;

[0015] c) Separation step: separation of the mixture M2 from step b) to obtain an inorganic-rich stream

[0016] M3 and inorganic-poor stream M4;

[0017] d) hydrothermal gasification step: hydrothermally gasifying the inorganic-lean stream M4 to obtain a mixture M5 comprising a gas and a liquid effluent;

[0018] e) a cooling and separation step: cooling and separating at least a portion of the mixture M5 produced by the hydrothermal gasification in step d) to separate gas from a liquid effluent M5' containing ammonia;

[0019] f) a possible ammonia enrichment step: subjecting at least a portion of the liquid effluent M5' to an ammonia enrichment treatment to obtain an ammonia-rich stream M5" and an ammonia-depleted stream M8;

[0020] g) a mixing step of mixing (i) at least a portion of the inorganic-rich stream M3 obtained in step c) and (ii) at least a portion of the liquid effluent M5' or, if any, at least a portion of the ammonia-rich stream M5" obtained in step f) to obtain a mixture M6;

[0021] h) a struvite formation step: forming struvite from at least a portion of the mixture M6 in a precipitation reactor;

[0022] i) Struvite recovery step: recovering struvite at the outlet of the precipitation reactor,

[0023] The treatment method comprises at least one step of injecting at least one magnesium salt into the mixture M1 before the pressurization step a) and / or during step g) and / or during step h) and / or into the mixture M6 between steps g) and h),

[0024] The mixing step g) can be carried out in a precipitation reactor if desired.

[0025] According to one embodiment of the method of the present invention, the magnesium salt is selected from magnesium hydroxide, magnesium oxide, magnesium chloride and mixtures thereof, preferably selected from magnesium hydroxide and magnesium oxide, and more preferably the magnesium salt is magnesium hydroxide.

[0026] According to one embodiment of the invention, the process comprises, upstream of step a), a hydrolysis step of mixture M1 carried out at a temperature ranging from 70 to 165° C. and a pressure ranging from 2 to 8 bar, making it possible to obtain a mixture M1h which is then pressurized in step a).

[0027] According to one embodiment of the invention, the method comprises a heat exchange between the mixture M5 coming from step d) and the mixture M1 or M1p or M1h upstream of the heating step b).

[0028] According to one embodiment of the method of the present invention, the mixture M1 contains solid matter in an amount of 5% to 50%, preferably 15% to 25%, by weight relative to the total weight of the mixture M1.

[0029] According to one embodiment of the process of the invention, the salt-rich stream produced from step c) contains phosphorus in a weight proportion preferably ranging from 1% to 20% relative to the total dry weight of the inorganic-rich stream M3.

[0030] According to one embodiment of the process according to the invention, the liquid effluent M5' comprises 1 g / l to 20 g / l of ammonia.

[0031] According to one embodiment of the process according to the invention, the ammonia enrichment step f) is carried out by using heat.

[0032] Preferably, the heat comes from the mixture M5 produced by hydrothermal gasification d).

[0033] According to one embodiment of the method of the present invention, the ammonia enrichment step f) can obtain an ammonia concentration in the liquid effluent M5" which is at least 1.5 times the ammonia concentration in the liquid effluent M5', preferably, the ammonia concentration in the liquid effluent M5" is at least 2 times the ammonia concentration in the liquid effluent M5', and even the ammonia concentration in the liquid effluent M5" is at least 5 times the ammonia concentration in the liquid effluent M5'.

[0034] According to one embodiment of the process of the invention, less than 75% by volume, preferably less than 50% by volume, of the liquid effluent M5' from step e) or, if step f) is performed, of the liquid effluent M5" from step f) is mixed during step g).

[0035] Another subject of the present invention is a device for implementing the treatment method according to the invention, comprising:

[0036] a pressure pump 3 supplied with the mixture M1 and comprising an outlet for the mixture M1p;

[0037] a heating device 2 comprising an inlet allowing the introduction of the mixture M1p (mixed if necessary with a magnesium salt Mg) and an outlet for the mixture M2;

[0038] a separation device 5 supplied with at least a portion of the mixture M2 and comprising an outlet for a stream rich in inorganics M3 and an outlet for a stream poor in inorganics M4;

[0039] a hydrothermal gasification reactor 8 supplied with at least part of the stream M4 coming from the separation device 5 and comprising an outlet for a mixture M5 comprising gas and liquid effluent;

[0040] a cooling and separation device 9 located downstream of the gasification reactor (8), supplied with at least a portion of the mixture M5 coming from the reactor 8 and comprising at least one outlet for a gaseous effluent and at least one outlet for a liquid effluent M5';

[0041] if necessary, an ammonia enrichment device 10 supplied with at least a portion of the liquid effluent M5 ′ and comprising an outlet for the enriched stream M5 ′ and an outlet for the depleted stream M8 ,

[0042] if necessary, a mixing device 6 supplied with (i) at least a portion of the flow M3 coming from the device 5 and (ii) at least a portion of the flow M5′ coming from the device 9 or at least a portion of the flow M5″ coming from the device 10 and comprising at least one outlet for the mixture M6,

[0043] - a precipitation reactor 7 comprising at least one inlet and at least one outlet, said precipitation reactor 7 being capable of being:

[0044] o or supplying: (i) at least a portion of the stream M3 from the separation device 5, and (ii)

[0045] at least a portion of the stream M5' coming from the cooling and expansion device 9 or at least a portion of the stream M5" coming from the enrichment device 10;

[0046] o or supply, if any, the stream M6 from the mixing device 6,

[0047] - at least one injection device located:

[0048] ○Upstream of the booster pump 3, and / or,

[0049] o in the mixing device 6, and / or,

[0050] o downstream of the mixing device 6 and upstream of the precipitation reactor 7, and / or,

[0051] o in the precipitation reactor 7.

[0052] According to one embodiment, the device according to the invention also comprises at least one hydrolysis reactor 4 upstream of the booster pump 3 , said hydrolysis reactor comprising at least one inlet for the mixture M1 and at least one outlet for the hydrolyzate M1h supplied to the booster pump 3 .

[0053] The present invention enables the recovery of phosphorus in the form of struvite from sludge generated by water treatment by a direct process with optimal yields, optimized thermal management and reduced formation of deposits in pipes.

[0054] The process of the invention also makes it possible to reduce the amount of heavy metals that can be recovered together with the phosphorus.

[0055] BRIEF DESCRIPTION OF THE DRAWINGS

[0056] [ Figure 1 ] is a schematic diagram of a processing method according to the present invention.

[0057] [ Figure 2 ] is a schematic diagram of a processing method according to the present invention.

[0058] [ Figure 3 ] is a schematic diagram of a processing method according to the present invention.

[0059] [ Figure 4 ] is a schematic diagram of a processing method according to the present invention.

[0060] [ Figure 5 ] is a schematic diagram of a processing method according to the present invention.

[0061] DETAILED DESCRIPTION OF THE INVENTION

[0062] The present invention relates to a method for treating a mixture M1 containing at least organic matter, the method comprising the following steps:

[0063] a. Pressurizing step: pressurizing the mixture M1 to a pressure of 150 to 300 bar, preferably 170 to 210 bar, to obtain a mixture M1p;

[0064] b. Heating step: heating the mixture M1p to 250°C to 500°C, preferably 350°C

[0065] to a temperature of 450° C., so as to obtain a mixture M2;

[0066] c. Separation step: separating the mixture M2 from step b), which step can obtain an inorganic-rich stream M3 and an inorganic-poor stream M4;

[0067] d. hydrothermal gasification step: hydrothermal gasification of the inorganic-lean stream M4 to obtain a mixture M5 comprising a gas and a liquid effluent containing water;

[0068] e. Cooling and separation step: cooling and separating at least a portion of the mixture M5 produced by the hydrothermal gasification in step d) to separate the gas from the liquid effluent M5' containing ammonia;

[0069] f possible ammonia enrichment step: at least a portion of the liquid effluent M5 'is subjected to ammonia enrichment treatment to obtain an ammonia-rich liquid stream M5 ";

[0070] g. Mixing step: Mix the following materials to obtain a mixture M6:

[0071] - at least a portion of the inorganic-rich stream M3 obtained in step c), and

[0072] at least a portion of the liquid effluent M5′ comprising ammonia or, if any, at least a portion of the enriched stream M5″ obtained in step f);

[0073] h. struvite formation step: forming struvite from at least a portion of the mixture of mixture M6 in a precipitation reactor;

[0074] i. Struvite recovery step: recovering struvite at the outlet of the precipitation reactor,

[0075] The treatment method comprises at least one injection step for injecting at least one magnesium salt into the mixture M1 before the pressurization step a) and / or during step g) and / or during step h) and / or into the mixture M6 between steps g) and h),

[0076] The mixing step g) can be carried out in a precipitation reactor if desired.

[0077] Within the meaning of the present invention, the expression "at least a portion of X" has the same meaning as the expression "all or a portion of X". When referring to a portion of a mixture, a stream or a gas, the expression refers to a certain proportion of said mixture, stream or gas. For example, within the meaning of this expression, "every portion of the mixture" or "every portion of the stream" or "every portion of the gas" will have the same composition.

[0078] Therefore, within the meaning of the present invention, the expression "step X carried out on the entire stream M coming from step Y" means that steps X and Y are consecutive and that there is no intermediate separation step between steps X and Y, but it is understood that there may be cooling / heating of stream M between steps X and Y, in particular by heat exchange, which may involve a stream exchange if necessary.

[0079] Mixture M1 containing at least organic matter

[0080] The mixture M1 contains at least organic matter. Typically, the mixture M1 also contains inorganic matter.

[0081] Among the inorganic substances, there may be mentioned salts containing anions, such as phosphates, sulfates, chlorides, carbonates and hydrogen carbonates, and having as counterions, for example, sodium, magnesium, calcium, ammonium and metals.

[0082] The mixture M1 can be selected, for example, from primary sludge, biological sludge, mixed sludge or digested sludge from municipal and industrial purification plants.

[0083] According to one embodiment, the mixture M1 contains 5% to 50% by weight of solid matter, preferably 15% to 25% by weight relative to the total weight of the mixture M1.

[0084] According to one embodiment, at least one magnesium salt is added to the mixture M1 so that magnesium is in a stoichiometric ratio or in excess stoichiometric ratio. Therefore, preferably, after adding the magnesium salt, the molar ratio of Mg / P in the mixture M1 is from 1 / 1 to 1.3 / 1.

[0085] Therefore, it may be provided that the phosphorus content in the mixture M1 is measured before subjecting the mixture M1 to the pressurization step a). In practice, the measurement of the phosphorus content is usually carried out at atmospheric pressure.

[0086] The addition of the magnesium salt is preferably carried out upstream of the pressurization step a).

[0087] The magnesium salt may be selected from magnesium hydroxide (Mg(OH)2), magnesium oxide (MgO) or magnesium chloride (MgCl2). Preferably, the magnesium salt is magnesium hydroxide.

[0088] The magnesium salt can be added to a mixing device which is supplied with a flow of the mixture M1 on the one hand and a flow of the magnesium salt on the other hand.

[0089] Possible hydrolysis step and possible grinding step

[0090] According to one embodiment, the process according to the invention comprises a hydrolysis step of the mixture M1 upstream of the pressurization step a).

[0091] The hydrolysis step may be carried out at a temperature of 70 to 165°C and a pressure of 2 to 8 bar.

[0092] The hydrolysis step allows reducing the viscosity of the mixture. The hydrolysis step thus makes it possible to obtain a mixture M1h, also called hydrolyzate.

[0093] The hydrolysis step allows the degradation of the organic matter, in particular it is able to break the chemical bonds and depolymerize the organic matter through the action of water.

[0094] The viscosity of the mixture M1h is typically at least 2 times lower, preferably at least 4 times lower, more preferably at least 10 times lower than the viscosity of the mixture M1.

[0095] Thus, the ratio of the viscosity of the mixture M1 to the viscosity of the mixture M1h is at least 2, preferably at least 4, more preferably at least 10.

[0096] The viscosity defined within the scope of the present invention is the viscosity measured at the same temperature (e.g. 20° C.) by using a rheometer suitable for the viscosity to be measured (cylinder-cylinder, plate-plate) and by measuring the viscosity at the same shear rate (in s -1 The kinematic viscosity is measured by measuring two viscosities under the conditions of 200 μm (in units), while usually taking care to eliminate turbulence problems and follow rheological rules (such as adjusting the spacing between cylinders according to the particle size).

[0097] The hydrolysis step carried out on the mixture M1 can be carried out in one or more hydrolysis reactors connected in parallel or in series.

[0098] The hydrolysis step makes it possible to hydrolyze the mixture M1, in particular by maintaining a mean hydraulic retention time at the desired temperature and pressure, preferably a temperature ranging from 70° C. to 165° C. and a pressure ranging from 2 bar to 8 bar, it being understood that if the hydrolysis step is carried out in a plurality of hydrolysis reactors, the temperature in the different reactors may be the same or different and, likewise, the pressure in the different reactors may be the same or different.

[0099] Advantageously, the hydrolysis step will be subject to an internal energy recovery step, so that the thermal energy consumption of the hydrolysis can be minimized. For example, there can be an energy recycling loop from the hot hydrolysate to the cold product to be hydrolyzed, for example by generating expansion vapor of the hot hydrolysate and injecting it into the cold product to be hydrolyzed or heat exchange.

[0100] At the outlet of the hydrolysis step, a hydrolysate M1h is obtained which is not necessarily at the temperature and pressure required for the hydrolysis. In fact, before leaving the hydrolysis step, the hydrolysate may, if desired, undergo a cooling and / or expansion step.

[0101] In particular, for example if the hydrolysis is carried out at high temperature, for example 100 to 165°C, it may be desirable to cool the hydrolysate, for example to a temperature below 90°C, so that stream M1h has a lower temperature for pressurization in step a) of the process of the invention.

[0102] The extraction of the hydrolysate M1h can be controlled by measuring the viscosity.

[0103] According to one embodiment, a controlled amount of steam can be injected into the hydrolysis reactor and diffused through the mixture M1. This control can be performed by measuring the temperature in the hydrolysis reactor. Thus, when the set temperature is reached, the steam injection can be stopped.

[0104] Steam can be:

[0105] - injection upstream of the hydrolysis into the inlet of a mixer of the dynamic mixer type, and / or

[0106] - direct injection into the hydrolysis reactor, preferably tangentially at the bottom to avoid clogging with sludge, and / or

[0107] - Injection into the recirculation loop of hydrolyzed sludge.

[0108] According to one embodiment, during the hydrolysis, the mixture M1 is mixed, for example stirred.

[0109] The hydrolysis reactor may be a batch reactor which may be stirred if desired.

[0110] According to one embodiment of carrying out the hydrolysis step, at least one magnesium salt is added to the mixture M1 to be treated before entering the hydrolysis unit.

[0111] According to another embodiment of carrying out the hydrolysis step, at least one magnesium salt is added to the mixture M1h downstream of the hydrolysis unit.

[0112] Prior to pressing, the treatment process may, if desired, include a grinding step, preferably mechanical grinding.

[0113] When there is a step of grinding the mixture M1, this step can be carried out before, during or after the hydrolysis (when there is a hydrolysis step). In the latter case, the mixture M1h will be ground.

[0114] When the method of the present invention implements a hydrolysis step in combination with a grinding step, the method of the present invention may, if desired, include a step of recycling at least a portion of the ground hydrolysate to the inlet of the hydrolysis step.

[0115] According to one embodiment, the hydrolysis reactor comprises a recirculation loop equipped with grinding means, making it possible to introduce at least a portion of the hydrolysate into said grinding means and to return at least a portion, preferably all, of the thus ground hydrolysate to the inlet of the hydrolysis step.

[0116] The purpose of this grinding step is to reduce the particle size of the mixture M1, typically such that the particle size of the solid fraction is less than 1000 μm, preferably less than 500 μm, more preferably less than 100 μm.

[0117] A particle size of "less than X μm" means that 95% of the solid particles can pass through a square mesh sieve of X μm, and the remaining 5% of the particles have a size no greater than 3 times of X μm.

[0118] Besides reducing the particle size to minimize downstream clogging, the grinding step enables homogenization of the mixture M1 and reduces the viscosity, which will allow better control of the process parameters of the hydrothermal gasification operation.

[0119] As with the hydrolysis step, grinding and particle size reduction also contribute to the homogenization of the biomass.

[0120] Mechanical stirring is difficult to carry out in reactors implementing high pressures, whereas the reduction in viscosity achieved as a result of the hydrolysis and grinding steps also makes it possible to improve the internal turbulence and therefore the homogenization in the pressurized reactor.

[0121] Pressurization step a)

[0122] The treatment method according to the invention comprises a step of pressurizing the mixture M1 , if desired previously mixed with at least one magnesium salt, to a pressure of 150 to 350 bar.

[0123] To implement the pressurization, a pump is provided at the beginning of the line upstream of the heating or, if present, at the outlet of the hydrolysis reactor.

[0124] The pump is arranged downstream of the mixing device so that the mixture M1 and the magnesium salt can be mixed.

[0125] The pressurized mixture M1 is denoted mixture M1p in the following.

[0126] Heating step b)

[0127] The treatment method according to the invention comprises a step of heating the mixture M1p to a temperature ranging from 250°C to 500°C.

[0128] The heating step can be carried out in a heating device. The device can be a continuous stirred tank reactor (CSTR) or a tubular flow reactor, also known as a plug-flow reactor. The reactor can be equipped with an external heating device or heated by exchange with a heat-carrying fluid.

[0129] The heating step makes it possible to obtain a mixture M2.

[0130] Thus, steps a) and b) make it possible to obtain a mixture M2 having a pressure ranging from 150 to 350 bar, preferably from 170 to 210 bar, and a temperature ranging from 250°C to 500°C, preferably from 350°C to 450°C.

[0131] Separation step c)

[0132] The process according to the invention comprises a step of separating the mixture M2 coming from step b) so as to obtain an inorganic-rich stream M3 and an inorganic-depleted stream M4.

[0133] Within the meaning of the present invention, the term "inorganic-rich stream" refers to a stream comprising therein an inorganic substance in a mass ratio greater than that of the mixture M2.

[0134] Within the meaning of the present invention, the term "inorganic-depleted stream" refers to a stream comprising a mass ratio of inorganic substances which is less than that of the mixture M2.

[0135] This separation step is typically carried out in a separation device comprising a line for conducting the mixture M2 produced in step a), and two outlet lines: (i) a line for withdrawing a stream M3 rich in inorganics and (ii) a line for withdrawing a stream M4 lean in inorganics.

[0136] The separation device may be a gravity separation device or a hydrodynamic separation device of the cyclone type, typically equipped with a continuous or intermittent discharge system at the bottom.

[0137] According to one embodiment, the mixture M1 contains phosphorus, and the inorganic-rich stream M3 from step c) contains at least 50% of the total weight of the phosphorus present in the mixture M1, in other words, at least 50% by weight of the phosphorus present in the mixture M1 is recovered into the inorganic-rich stream M3 from step c).

[0138] According to one embodiment, the mixture M1 comprises phosphorus, while the salt-rich stream M3 from step c) comprises phosphorus in a weight ratio preferably ranging from 1% to 20% relative to the total dry weight of the inorganic-rich stream M3.

[0139] Possible pressurization step and possible heating step

[0140] According to one embodiment, the treatment method according to the invention comprises an additional pressurization step carried out on the flow M4 upstream of the hydrothermal gasification step.

[0141] According to this embodiment, preferably, the pressurization step a) is carried out at a pressure comprised between 150 and 210 bar, whereas the additional pressurization step enables the mixture M4 coming from step c) to reach a pressure greater than or equal to 225 bar.

[0142] The hydrothermal gasification processes of the prior art operate at a single operating pressure. According to an advantageous embodiment of the invention, the process of the invention is implemented at two operating pressures. This dual-pressure operation allows for a number of advantages.

[0143] On the one hand, only a portion of the device is exposed to very high pressure (only the "second portion" after additional pressurization), thus reducing construction costs and installation constraints.

[0144] On the other hand, when recovering heat from stream M5 to preheat the mixture M1, M1p or M1h, the pressure difference between the two streams makes it possible to maintain a greater temperature difference (ΔT) than when the two pressures are the same, which is beneficial to heat exchange. This enables ΔT to provide a greater driving force for heat exchange in the exchanger and therefore enables the use of a smaller exchanger.

[0145] According to one embodiment, the treatment method according to the invention further comprises a step of heating the stream M4, preferably to a temperature greater than or equal to 300°C, more preferably to a temperature between 400°C and less than 600°C.

[0146] When the process comprises an additional pressurizing step, then preferably the process also comprises the step of heating stream M4, preferably at a temperature of from 400°C to less than 600°C.

[0147] This additional heating step may be carried out in a heating device selected from electrical heating or indirect heating by hot gases generated by combustion.

[0148] Hydrothermal gasification step d)

[0149] The treatment method according to the invention comprises a step of hydrothermal gasification of the inorganic-lean stream M4 in order to obtain a mixture M5 comprising gas and an aqueous effluent.

[0150] Hydrothermal gasification (GH) is a thermal depolymerization process used to convert organic matter present in a moist medium into a mixture consisting only of small molecules at high to moderate temperatures and pressures.

[0151] In the GH process, carbon and hydrogen of organic materials are thermochemically converted under quasi-critical or supercritical conditions. Part of the conversion is into water-soluble low-molar-mass compounds.

[0152] The other part is converted into gaseous products, such as carbon dioxide (CO2), methane (CH4), hydrogen (H2), carbon monoxide (CO), light hydrocarbons such as ethane (C2H6) and propane (C3H8).

[0153] When staying in a hydrothermal gasification reactor at temperatures below 400 ° C, the organic matter undergoes, among other reactions, a decomposition based on hydrolysis, similar to the reactions that occur during liquefaction, but at a much faster rate. In fact, carrying out the reaction under quasi-critical or supercritical conditions makes it possible to exploit the unique properties of supercritical water as a solvent, which allow conditions of solvation and homogeneous reactions, thus obtaining very high reaction kinetic rates. It is thus possible to use much shorter residence times and much higher heating rates than in conventional hydrolysis, limiting or even avoiding condensation and polymerization side reactions that lead to the formation of bio-oil and biochar.

[0154] When the GH is operated at temperatures above 400 °C, free radical decomposition of the polymer (particularly reactions involving decarboxylation, deamination via C-N bond cleavage, and C-C or C-O cleavage) dominates, while endothermic steam reforming is the main reaction pathway for converting small molecules containing 1 to 3 carbon atoms into carbon oxides and dihydrogens and for converting nitrogen into ammonia.

[0155] Methane is also produced by methanation of CO and CO2 using dihydrogen.

[0156] Therefore, GH can be considered as a decomposition process that transforms the organic residues in stream M4 into more easily biodegradable substances and ammonia dissolved in the liquid phase.

[0157] The treatment conditions for GH (in particular temperature, pressure and, to a lesser extent, residence time) can be adjusted in order to produce not only a gaseous fraction (synthesis gas) containing CH4, CO, CO2 and H2, but also an aqueous effluent which contains, on the one hand, predominantly easily digestible compounds, in particular carboxylic acids, and, on the other hand, predominantly ammonia in the form of ammonium salts of the produced carbonic acid.

[0158] It should be noted that GH is different from hydrothermal liquefaction (HTL), in particular because the conversion and decomposition levels of organic matter in HTL are not as high as in GH, even when GH is used under moderate temperature conditions.

[0159] Under HTL conditions, water still contains HO- and H3O+ ions that initiate the hydrolysis of organic matter.

[0160] The hydrolysis takes place only on the surface of the cellulose compounds contained in the organic part, which is very poorly soluble in the subcritical medium, giving a rather low decomposition conversion.

[0161] Condensation reactions of intermediates (mainly including aldol condensation, alkylation or Friedel-Craft acylation) are important reaction pathways leading to the formation of biocrude oil, which is an oil that can be used as a fuel (also called bio-oil), i.e., the biocrude oil contains organic molecules containing 5 or more carbon atoms, typically 8 to 16 carbon atoms. In contrast, the liquid products of GH contain mainly compounds that are easily biodegradable.

[0162] GH differs from pyrolysis in that it is carried out in an aqueous medium, where the water is in a supercritical or quasi-critical state.

[0163] GH differs from "conventional" gasification of organic matter in that "conventional" gasification reduces the carbon / hydrogen mass ratio (C / H), resulting in products of high calorific value, including gases consisting primarily of syngas (a mixture of H2 / CO), bio-oils and / or carbonaceous solids (char).

[0164] In the treatment method according to the invention, the hydrothermal gasification step is generally carried out in a hydrothermal gasification reactor which is supplied at the inlet with at least a portion of the inorganic-lean stream M4 and comprises an outlet M5, the inorganic-lean stream M4 may come directly from the separation device or from a possible additional heating step carried out on at least a portion of the stream M4.

[0165] According to one embodiment, the gasification reactor is a tubular reactor.

[0166] Preferably, the hydrothermal gasification step is carried out at a temperature below 600°C, preferably at a temperature of 350°C to less than 600°C, more preferably at a temperature of 450 to less than 600°C.

[0167] Preferably, the hydrothermal gasification step is carried out at a pressure greater than or equal to 220 bar, preferably greater than or equal to 250 bar.

[0168] Preferably, the (total) residence time of the inorganic-lean stream M4 in GH step d) is generally from 1 minute to 20 minutes, preferably from 2 minutes to 10 minutes, more preferably from 3 to 5 minutes.

[0169] According to a preferred embodiment, the hydrothermal gasification step is carried out in the presence of a catalyst. Preferably, the catalyst is chosen from metals on activated carbon, such as metals of the ruthenium, nickel, palladium or platinum type.

[0170] The catalyst may be in the form of a bed of solid particles within the gasification reactor.

[0171] Since separation step c) of the process according to the invention enables the removal of so-called "poison" compounds, the catalyst possibly used in the hydrothermal gasification step is not degraded by these harmful compounds which could damage, in particular lead to deactivation of, the catalyst.

[0172] Cooling and separation step e)

[0173] The treatment process according to the invention comprises a step of cooling and separating at least part of the mixture M5 resulting from the hydrothermal gasification of step d) so as to obtain a gaseous effluent and a liquid effluent comprising ammonia.

[0174] The cooling step may bring the mixture M5 to a temperature lower than or equal to 200°C, preferably lower than or equal to 120°C, preferably from 50 to 120°C.

[0175] The cooling device may be selected from a heat exchanger, a flash evaporator, a scrubber, a Rankine cycle.

[0176] The separation step can be carried out in an expansion system so that a liquid effluent M5' is obtained on the one hand and a gaseous effluent on the other hand.

[0177] According to one embodiment, the liquid effluent M5' comprises 1 g / l to 20 g / l of ammonia.

[0178] Possible ammonia enrichment step f)

[0179] According to one embodiment, the treatment method according to the invention comprises a step of enriching at least part of the liquid effluent M5' comprising ammonia from step e) with ammonia in order to obtain an ammonia-rich stream M5" and an ammonia-depleted stream M8.

[0180] Within the meaning of the present invention, the term “ammonia-rich stream” refers to such a stream which comprises a higher proportion of ammonia than that of the liquid effluent M5 ′.

[0181] Within the meaning of the present invention, the term “ammonia-lean stream” refers to such a stream which comprises a lower proportion of ammonia than the proportion of ammonia of the liquid effluent M5 ′.

[0182] According to one embodiment, the ratio of the ammonia concentration in the enriched stream M5″ to the ammonia concentration in the input effluent M5′ is at least 1.5, preferably at least 2, and more preferably at least 5.

[0183] According to one embodiment, the ammonia-rich stream produced from step f) comprises from 1 g / l to 20 g / l of ammonia.

[0184] According to one embodiment, the ammonia-poor stream M8 can be sent to a digester for a digestion step.

[0185] The enrichment step can be carried out in an enrichment device, which can be composed of, for example, one or more evaporation concentration reactors, or one or more membrane reactors or stripping reactors.

[0186] Therefore, according to an advantageous embodiment, when the enrichment step is carried out, a cooling and separation step e) is preferably carried out so as to bring the liquid effluent M5' to a temperature ranging from 75° C. to 200° C., preferably from 100° C. to 120° C. In fact, according to this embodiment, heat is advantageously retained to improve the yield during the enrichment step.

[0187] According to one embodiment, the ammonia enrichment step f) is carried out by using heat, preferably heat recovered from the mixture M5 produced from the hydrothermal gasification d).

[0188] According to one embodiment, the heat present in the mixture M5 from step d) is recovered, said recovered heat preferably being able to at least partially heat the mixture M1 during step a).

[0189] Preferably, this heat recovery is carried out by heat exchange between the mixture M5 coming from step d) and the mixture M1 or M1h upstream of the heating step b).

[0190] When the hydrolysis is carried out, heat exchange can be carried out between mixture M5 and mixture M1 so that mixture M1 can be heated for the hydrolysis step, or heat exchange can be carried out between mixture M5 and mixture M1h so that mixture M1h can be heated for the heating step b).

[0191] Thus, mixture M1 or M1h can recover heat from mixture M5, which will make it possible to reduce the energy requirement of the process and to cool mixture M5.

[0192] Typically, the ammonia demand for the formation of struvite is generally lower than the amount of ammonia in the liquid effluent M5' or liquid effluent M5", and therefore, preferably only a portion of the stream M5' of the liquid effluent or the enriched stream M5" of the liquid effluent is mixed with at least a portion of the stream M3 during step g). For example, less than 75% of the volume of M5' or M5", or even less than 50% of the volume of M5' or M5", may be used during the mixing step g).

[0193] Mixing step g)

[0194] The treatment method according to the invention comprises a step of mixing at least part of the inorganic-rich stream M3 obtained at the end of step c) with at least part of the liquid effluent comprising ammonia obtained at the end of step e) or of step f) (when this step f) is present) to obtain a mixture M6.

[0195] According to one embodiment, the entirety of the inorganic-rich stream M3 obtained at the end of step c) is mixed during this step g).

[0196] According to one embodiment, the entirety of the liquid effluent comprising ammonia obtained at the end of step e) or step f) (when step f) is present) is mixed during this step g).

[0197] The mixing step g) is preferably carried out in a mixing device. The mixing device can be a batch, semi-continuous or continuous reactor, which is stirred by a stirring system of the blade, screw stirrer, draft tube type or by external reactor recirculation. The reactor is equipped with a pH measuring device and an alkali and acid injection device, so that the pH value can be controlled.

[0198] Preferably, the pH of the reactor is adjusted so that the pH is between 7.5 and 10, preferably between 8 and 9 at ambient temperature.

[0199] The mixing step g) is typically carried out at a temperature ranging from 50°C to 250°C and / or at a pressure ranging from 1 bar to 200 bar.

[0200] This mixing step can, if desired, be carried out in a struvite-forming precipitation reactor.

[0201] Therefore, according to this embodiment, at least part of the inorganic-rich stream M3 obtained at the end of step c) and at least part of the liquid effluent containing ammonia obtained at the end of step e) or step f) (when step f) is present) are introduced into a precipitation reactor, and the mixture M6 is formed in situ in the precipitation reactor, and the struvite formation step, i.e. step h), is carried out.

[0202] According to one embodiment, at least one magnesium salt is injected in the following manner:

[0203] - injected into the mixture during step g), and / or,

[0204] - when steps g) and h) are carried out in different apparatuses, injected into the mixture M6 between steps g) and h), and / or,

[0205] - when carried out in a precipitation reactor, during step g).

[0206] The magnesium salt may be selected from magnesium hydroxide (Mg(OH)2), magnesium oxide (MgO) or magnesium chloride (MgCl2). Preferably, the magnesium salt is magnesium hydroxide.

[0207] According to one embodiment, at least one magnesium salt is added so that the magnesium is in a stoichiometric or superstoichiometric ratio. Thus, preferably, after adding the magnesium salt, the Mg / P molar ratio in the mixture M6 is from 1 / 1 to 1.3 / 1.

[0208] Thus, the phosphorus content of the mixture M1 can be measured before it is used in the pressurization step a). In practice, the measurement of the phosphorus content is usually carried out at atmospheric pressure. Such a measurement carried out in the mixture M1 will allow a good estimation of the phosphorus content in the mixture M6.

[0209] Measuring the phosphate content in the liquid effluent M7 also enables the adjustment of the magnesium salt content that needs to be added to the mixture M6.

[0210] The magnesium salt can be added to the mixing device during step g) and / or to the mixture M6 downstream of said mixing device.

[0211] The mixing step g) can be carried out directly in the precipitation reactor.

[0212] According to this embodiment, the precipitation reactor is supplied, on the one hand, with at least a portion of the inorganically rich stream M3 obtained at the end of step c) and, on the other hand, with:

[0213] - at least a portion of the liquid effluent M5' comprising ammonia obtained at the end of step e), or

[0214] - when step f) is present, at least a portion of the enriched stream M5" obtained at the end of step f).

[0215] According to this embodiment, the mixture is also referred to as mixture M6.

[0216] According to this embodiment, the magnesium salt may be added to the precipitation reactor.

[0217] According to one embodiment of the present invention, the treatment method comprises the following magnesium salt injection step:

[0218] - injecting a magnesium salt, preferably selected from MgO and Mg(OH)2 and mixtures thereof, into the mixture upstream of the pressurization step a), and

[0219] - a magnesium salt preferably chosen from MgCl2 is injected into the mixture during step g) and / or during step h) and / or, when steps g) and h) are carried out in different apparatuses, a magnesium salt preferably chosen from MgCl2 is injected into the mixture M6 between step g) and step h).

[0220] Struvite formation step h)

[0221] The treatment method according to the invention comprises a step of forming struvite from at least part of the mixture M6 of step g) in a precipitation reactor.

[0222] The struvite forming step may be carried out at a temperature of 20°C to 250°C and / or a pressure of 1 to 200 bar.

[0223] According to one embodiment, the entire mixture M6 from step g) will be used during the struvite formation step i). Of course, when the mixing step g) is carried out in a precipitation reactor, the entire mixture M6 will necessarily be used during the struvite formation step i).

[0224] When the mixing step g) is carried out in a different apparatus than the precipitation reactor, at least a portion of the mixture M6, preferably the entirety of the mixture M6, is injected into the precipitation reactor to carry out step i).

[0225] The precipitation reactor can be an infinite mixing reactor or a fluidized bed reactor. An example of a commercial precipitation reactor that is particularly useful for precipitating phosphorus in the form of struvite is

[0226] At the end of step h), the struvite is recovered, after possible decantation.

[0227] It should be noted that, in addition to the struvite, this step h) will produce a further effluent, which will be the liquid effluent M7.

[0228] The invention also relates to an apparatus for carrying out the method of the invention.

[0229] The device according to the invention comprises:

[0230] a pressure pump 3 which is supplied with the mixture M1 and comprises an outlet for the mixture M1p,

[0231] a heating device 2 comprising an inlet allowing the introduction of a mixture M1p which can be mixed if desired with a magnesium salt Mg and comprising an outlet for the mixture M2,

[0232] a separation device 5 supplied with at least a portion of the mixture M2 and comprising an outlet for a stream rich in inorganics M3 and an outlet for a stream poor in inorganics M4,

[0233] a hydrothermal gasification reactor 8 supplied with at least part of the flow M4 coming from the separation device 5 and comprising an outlet for a mixture M5 comprising gas and liquid effluent,

[0234] a cooling and separation device 9 located downstream of the gasification reactor, supplied with at least a portion of the mixture M5 and comprising at least one outlet for a gaseous effluent and at least one outlet for a liquid effluent M5',

[0235] a possible ammonia enrichment device 10 supplied with at least a portion of the liquid effluent M5 ′ and comprising an outlet for the enriched stream M5 ′ and an outlet for the depleted stream M8 ,

[0236] a possible mixing device 6 supplied with (i) at least a portion of the flow M3 and (ii) at least a portion of the flow M5′ or at least a portion of the flow M5″ and comprising an outlet for the flow M6,

[0237] - a precipitation reactor 7 comprising at least one inlet and at least one outlet, said precipitation reactor 7 being capable of being:

[0238] o or supply: (i) at least a portion of the stream M3 coming from the separation device 5, and (ii) at least a portion of the stream M5' coming from the cooling and expansion device 9 or at least a portion of the stream M5" coming from the enrichment device 10;

[0239] o or supplying a stream M6 from a mixing device 6,

[0240] - at least one injection device located:

[0241] ο upstream of the booster pump 3, and / or,

[0242] o When a mixing device 6 is present, in the mixing device 6, and / or,

[0243] o when a mixing device 6 is present, downstream of the mixing device 6 and upstream of the precipitation reactor 7, and / or,

[0244] o in the precipitation reactor 7.

[0245] According to one embodiment, the device also comprises at least one hydrolysis reactor 4 upstream of the booster pump 3 , said hydrolysis reactor comprising at least one inlet for the mixture M1 and at least one outlet for the hydrolyzate M1h supplied to the booster pump 3 .

[0246] According to one embodiment, the precipitation reactor 7 can be supplied with: (i) at least a portion of the flow M3 coming from the separation device 5 and (ii) at least a portion of the flow M5 ′ coming from the cooling and expansion device 9 or at least a portion of the flow M5 ″ coming from the enrichment device 10 .

[0247] According to this embodiment, the mixing step g) is carried out in the precipitation reactor 7 in which the struvite formation step i) is carried out.

[0248] According to another embodiment, the apparatus comprises a mixing device 6 distinct from the precipitation reactor 7. The mixing device 6 is then supplied with: (i) at least a portion of the stream M3 and (ii) at least a portion of the stream M5' or at least a portion of the stream M5". And the mixing device 6 comprises an outlet for the stream M6. According to this embodiment, the precipitation reactor 7 is supplied with the stream M6 from the mixing device 6.

[0249] Figures 1 to 3 Each shows an embodiment of the device according to the invention and the method according to the invention, but does not limit the scope of the invention.

[0250] like Figure 1 As shown, the mixture M1 to which magnesium salt Mg is added as needed is first pressurized by a pressure pump 3, and then passes through a heating device 2, wherein the mixture M1 is usually pressurized to a pressure of 150 to 350 bar, and the mixture is referred to as M1p, and then heated to a temperature of 250 to 500° C. A mixture M2 is obtained at the outlet of the heating device 2.

[0251] like Figure 1 As shown, the mixture M2 is supplied to a separation device 5 so that an inorganic-rich stream M3 and an inorganic-lean stream M4 can be obtained.

[0252] like Figure 1 As shown, the stream M4 is supplied to a hydrothermal gasification reactor 8 to obtain a mixture M5 comprising gas and liquid effluent. The gasification reactor 8 may comprise a catalyst.

[0253] like Figure 1 As shown, the mixture M5 is supplied to a cooling and separation device 9 capable of cooling the mixture M5 to a temperature lower than or equal to 200° C. and obtaining a gaseous flow and a liquid effluent M5 ′.

[0254] like Figure 1 As shown, the device comprises a mixing device 6 which is supplied, on the one hand, with the flow M3 and, on the other hand, with at least a part of the flow M5 ′ output from the cooling and separation device 9 .

[0255] like Figure 1 As shown, the mixture M6 from the mixing device, possibly with the addition of magnesium salt (Mg), is then introduced into the precipitation reactor 7.

[0256] The struvite is then recovered downstream of the precipitation reactor 7 , after a possible decantation (not shown), together with the liquid effluent M7 .

[0257] It should be noted that the device according to the invention may include other elements not shown in the figures. In particular, the device according to the invention may include valves and diverter lines so that only a portion of the flow can be introduced instead of the entire flow, as shown in the figures for simplicity, in particular for flows M3, M4, M5 or M6.

[0258] Control elements may also be provided to control the flow rate of the stream.

[0259] The figures show multiple steps for adding magnesium salt, but it should be noted that the apparatus according to the invention may include a single device or multiple devices allowing the addition of magnesium salt. Such a device may include a magnesium salt storage tank and a supply line for guiding the magnesium salt from the tank to the injection location.

[0260] Figure 2 The embodiment shown is similar to Figure 1 The embodiment of is different in that an enrichment device 10 is present, which is located downstream of the cooling device 9 and upstream of the mixing device 6 .

[0261] The enrichment device 10 comprises an inlet for at least a portion of the liquid effluent M5' and an outlet for the enriched effluent M5" and an outlet for the depleted effluent M8.

[0262] According to this embodiment, the device according to the invention preferably comprises a bypass valve making it possible to control the amount of effluent M5 ″ introduced into the mixing device 6 .

[0263] Figure 3 The embodiment shown is similar to Figure 2 The embodiment of FIG. 4 differs in that a hydrolysis reactor 4 is present upstream of the pressure pump 3 .

[0264] According to one embodiment of the invention, the apparatus comprises at least one hydrolysis reactor 4 upstream of the booster pump 3 .

[0265] In practice, the plant according to the invention may comprise one or more hydrolysis reactors 4 connected in series or in parallel, fed at the inlet through a feed line of the mixture M1 and discharged through an outlet line of the hydrolyzed mixture M1h at a temperature lower than or equal to the hydrolysis temperature. The hydrolysis reactors 4 advantageously comprise heating and pressurizing means and possibly stirring means, and advantageously also internal heat recovery means.

[0266] According to this embodiment, the pump 3 is supplied with the mixture M1h.

[0267] According to this embodiment, it can be arranged that the magnesium salt is injected upstream or downstream of the hydrolysis reactor 4 .

[0268] The hydrolysis reactor 4 can, if necessary, be provided with a grinding device upstream thereof, or be equipped with a recirculation circuit having a grinding device, or a grinding device can be provided downstream thereof upstream of the pump 3 .

[0269] according to Figure 4 In one embodiment shown, the precipitation reactor 7 is supplied with: (i) at least a portion of the stream M3 coming from the separation device 5, and (ii) at least a portion of the liquid effluent M5' coming from the cooling and expansion device 9. According to this embodiment, the magnesium salt can be injected into the precipitation reactor 7 and / or into the mixture M1 or M1h (in the case of a hydrolysis reaction not carried out upstream of the pressurization by the pump 3). Figure 4 , but is part of the present invention).

[0270] according to Figure 5 In one embodiment shown, the precipitation reactor 7 is supplied with: (i) at least a portion of the stream M3 coming from the separation device 5, and (ii) a portion of the stream M5″ coming from the enrichment device 10. According to this embodiment, the magnesium salt can be injected into the precipitation reactor 7 and / or into the mixture M1 or M1h.

[0271] The device according to the invention may of course comprise one or more of the features described within the scope of the method according to the invention.

Claims

1. A method for treating a mixture M1 containing at least organic matter, the method comprising the following steps: a) a pressurizing step: pressurizing the mixture M1 to a pressure of 150 to 300 bar, preferably 170 to 210 bar, to obtain a mixture M1p; b) a heating step: heating the mixture M1p to a temperature of 250° C. to 500° C., to allow obtaining a mixture M2; c) separation step: separating the mixture M2 from the step b) to obtain an inorganic-rich stream M3 and an inorganic-poor stream M4; d) hydrothermal gasification step: hydrothermally gasifying the inorganic-lean stream M4 to obtain a mixture M5 comprising a gas and a liquid effluent; e) a cooling and separation step: cooling and separating at least a portion of the mixture M5 produced by the hydrothermal gasification of step d) to separate gas from a liquid effluent M5' containing ammonia; f) a possible ammonia enrichment step: subjecting at least a portion of the liquid effluent M5' to an ammonia enrichment treatment to obtain an ammonia-rich stream M5" and an ammonia-depleted stream M8; g) a mixing step of mixing (i) at least a portion of the inorganic-rich stream M3 obtained in step c) and (ii) at least a portion of the liquid effluent M5' or at least a portion of the enriched stream M5" obtained in step f), if any, To obtain a mixture M6; h) a struvite formation step: forming struvite from at least a portion of the mixture M6 in a precipitation reactor; i) Struvite recovery step: recovering struvite at the outlet of the precipitation reactor, The treatment method further comprises at least one injection step of injecting at least one magnesium salt into the mixture M1 before the pressurization step a) and / or during the step g) and / or during the step h) and / or into the mixture M6 between the steps g) and h), The mixing step g) can be carried out in the precipitation reactor if desired.

2. The processing method according to claim 1, wherein: The magnesium salt is selected from magnesium hydroxide, magnesium oxide, magnesium chloride and mixtures thereof, preferably selected from magnesium hydroxide and magnesium oxide, and more preferably the magnesium salt is magnesium hydroxide.

3. Process according to any one of claims 1 to 2, comprising, upstream of step a), a hydrolysis step of hydrolyzing the mixture M1 at a temperature ranging from 70° C. to 165° C. and a pressure ranging from 2 bar to 8 bar so as to obtain a mixture M1h which will subsequently be pressurized in step a).

4. Process according to any one of claims 1 to 3, comprising a heat exchange between the mixture M5 coming from step d) and the mixture M1 or M1p or M1h upstream of the heating step b).

5. The processing method according to any one of claims 1 to 4, wherein: The mixture M1 contains solids in an amount of 5% to 50% by weight, preferably 15% to 25% by weight relative to the total weight of the mixture M1.

6. The processing method according to any one of claims 1 to 5, wherein: Said salt-rich stream coming from said step c) comprises phosphorus in a weight proportion preferably ranging from 1% to 20% relative to the total dry weight of said inorganic-rich stream M3.

7. The processing method according to any one of claims 1 to 6, wherein: The liquid effluent M5' comprises 1 g / l to 20 g / l of ammonia.

8. The processing method according to any one of claims 1 to 7, wherein: The ammonia enrichment step f) is performed by using heat.

9. The processing method according to claim 8, wherein: The heat comes from the mixture M5 generated by the hydrothermal gasification d).

10. The processing method according to any one of claims 1 to 9, wherein: The ammonia enrichment step f) makes the ammonia concentration in the liquid effluent M5" at least 1.5 times the ammonia concentration in the liquid effluent M5', preferably the ammonia concentration in the liquid effluent M5" is at least 2 times the ammonia concentration in the liquid effluent M5', or even the ammonia concentration in the liquid effluent M5" is at least 5 times the ammonia concentration in the liquid effluent M5'.

11. The processing method according to any one of claims 1 to 10, wherein: Less than 75% by volume, preferably less than 50% by volume of the liquid effluent M5' from step e) or, if step f) is performed, the liquid effluent M5" from step f) is mixed during step g).

12. A device for implementing the treatment method according to any one of claims 1 to 11, the device comprising: a pressure pump (3) supplied with said mixture M1 and comprising an outlet for said mixture M1p; - a heating device (2) comprising an inlet allowing the introduction of said mixture M1p, possibly mixed with a magnesium salt Mg, and comprising an outlet for said mixture M2; a separation device (5) supplied with at least a portion of said mixture M2 and comprising an outlet for a stream rich in inorganics M3 and an outlet for a stream poor in inorganics M4; a hydrothermal gasification reactor (8) supplied with at least part of the flow M4 coming from said separation device 5 and comprising an outlet for a mixture M5 comprising gas and liquid effluent; a cooling and separation device (9) located downstream of said gasification reactor (8), supplied with at least a portion of said mixture M5 coming from said reactor (8) and comprising at least one outlet for a gaseous effluent and at least one outlet for a liquid effluent M5'; - a possible ammonia enrichment device (10) supplied with at least part of said liquid effluent M5' and comprising an outlet for said enriched stream M5' and for said depleted stream M8; - a possible mixing device (6) supplied with (i) at least part of said flow M3 coming from said device (5) and (ii) at least part of said flow M5' coming from said device (9) or at least part of said flow M5" coming from said device (10), and comprising at least one outlet for said mixture M6; - a precipitation reactor (7) comprising at least one inlet and at least one outlet, said precipitation reactor (7) being operable by: o or supplying: (i) at least a portion of the stream M3 coming from the separation device (5), and (ii) at least a portion of the stream M5' coming from the cooling and expansion device (9) or at least a portion of the stream M5" coming from the enrichment device (10); o or supplying, if any, said stream M6 from said mixing device (6); - at least one injection device located: ο upstream of the booster pump (3), and / or, o In the mixing device (6), and / or, o downstream of the mixing device (6) and upstream of the precipitation reactor (7), and / or, ○In the precipitation reactor (7).

13. The apparatus according to claim 12, further comprising at least one hydrolysis reactor (4) upstream of the booster pump (3), the hydrolysis reactor comprising at least one inlet for the mixture M1 and at least one outlet for the hydrolyzate M1h, the hydrolyzate M1h being supplied to the booster pump (3).

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